In the operation of electronic timing systems for modern glass container forming machines, it has become important that the precise time of arrival of an individual gob of molten glass at the molds be detected. With the advent of glass forming machines in which the machine may have as many as ten independent sections with each section having four parison molds, the success of operating the machine in the most efficient manner so that there will not be excessive periods of dead time when being advanced, requires that the time of arrival of each individual gob at its parison mold be known with precision.
The gob arrival will in many cases dictate the precise instant when the next step in the forming process may be started. The mechanisms that come into play, such as removal of a guide funnel and seating of a baffle, all require that the gob of glass will have arrived at the mold. In many of the multiple cavity machines where the mechanisms operate in unison, because they are all physically interrelated, requires that the "last to arrive" of the plurality of gobs in a single section be known with precision.
In the past, and as disclosed in U.S. Pat. No. 4,162,909 issued July 31, 1979, the gob arrival sensors consisted of a phototransistor mounted in a housing made of a phenolic material, with an opening of about one-eighth inch in the housing serving as the "window" through which the gob path is viewed. A standard BNC connector is connected to the housing. The connection from connector to the machine logic and timing circuits is not revealed.
In a glass forming machine of the type which forms gobs of molten glass into articles such as bottles will normally have the gobs fed to it by gravity from an overhead gob former and feeder. The gobs, as they are made, will be distributed to the sections of the machine in a predetermined sequence, and in the travel of an individual gob to a particular parison mold, the gob is normally guided to the central axis of the mold by a generally vertical gob guide. An example of a gob guide is that shown in U.S. Pat, No. 3,585,018 dated June 15, 1971 as element 11. In some machines the gob may fall through a curved deflector just prior to entry into the mold. In the present case the term gob guide is to include any gob directing means which is just in advance of the parison mold.
One of the most critical deficiencies in existing gob sensing systems is that they are subject to failure because of the hostile environment in which they are required to operate and the lack of protection for the sensor, as well as the accessing equipment, including leads from the sensor to the section computer.